In particular, test that serialization is not dependent on the
locale.

This functionality was lost when GdkRGBA was introduced.

Bug 632936

After these changes, GtkCalendar only has a few input-only windows
left for catching input events. All drawing goes to the parent
window now.

Double-click to mark/unmark was lost a while ago.

Also add easy RTL testing.

Remove no-longer-needed vfuncs, no longer existing functions,
and improve the docs here and there.

It didn't quite turn out as I wanted it.
I'll put it in bug 619148 for now.

The scrollable patch removed set_scroll_adjustments (NULL, NULL) from
gtk_tree_view_init() which ensured the treeview would have adjustments
at all times, this patch adds set_v/hadjustment (NULL) to _init to ensure
the same thing (without it, there are crashes when trying to access the
adjustments notably from set_headers_visible() in gedit).

I.e. Since we are now calling get_preferred_width() to ensure a good 'for_size'
for get_height_for_width() we need to avoid warning about this internal expected
recursion.

This will let us use combo boxes as property editors for
GSettings enmerations easily.

These properties use GdkRGBA to render the cell renderer's content.
Note that Pango attributes are used to render the foreground color,
so the alpha value is currently ignored.

This property uses GdkRGBA in order to render the cell renderer's
background.

The hook to change the global palette is still unchanged, it is quite
tied to GdkColor and the color format used to store the palette in
GtkSettings.

A ::background-rgba property was also added, this API is meant
to replace the gtk_cell_view_set_background_color() call.

This new function takes a GdkRGBA in order to set the background to
an alpha color. Keep in mind that RGBA visuals and a composited environment
are still necessary to have an alpha background displayed.